Room Temperature Deformation in “Soft” Orientation Nial Single Crystals

1990 ◽  
Vol 213 ◽  
Author(s):  
R.D. Field ◽  
D.F. Lahrman ◽  
R. Darolia
Keyword(s):  
Shear Stress ◽  
Elevated Temperature ◽  
Single Crystals ◽  
Room Temperature ◽  
Dislocation Motion ◽  
Temperature Deformation ◽  
Slip Planes ◽  
Schmid Factor ◽  
Critical Resolved Shear Stress ◽  
Active Slip

ABSTRACTA detailed study of deformation of NiAl single crystals in two soft orientations, <110> and <111>, has been conducted. The Schmid factor favors {100} slip in the former and {110} slip in the latter. Detailed dislocation analysis, critical resolved shear stress measurements, and slip trace analysis have been performed to determine the nature of dislocation motion and interactions in this material. Particular attention is given to prismatic loops formed during deformation, since the shapes of these loops reveal the active slip planes. Similar loop morphologies observed in elevated temperature [001] oriented tensile specimens are also discussed.

Plastic Deformations in L10-Ordered Single Crystals with their c/a Ratios Less than Unity

2007 ◽  
Vol 561-565 ◽  
pp. 459-462
Author(s):  
Katsushi Tanaka ◽  
Hiromitsu Ide ◽  
Yoshinori Sumi ◽  
Kyosuke Kishida ◽  
Haruyuki Inui
Keyword(s):  
Shear Stress ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Room Temperature ◽  
The Other ◽  
Compressive Deformation ◽  
Positive Temperature ◽  
Plastic Deformations ◽  
Temperature Range ◽  
Critical Resolved Shear Stress

Compressive deformation of L10-ordered single crystals of FePd whose c/a ratio less than unity have been investigated from room temperature to 823 K. The results show that the critical resolved shear stress (CRSS) for octahedral glide of ordinary dislocations is smaller than that of super-lattice dislocations in all the temperature range investigated, that is the opposite sense to the case of Ti-56 mol% Al. The CRSS for ordinary dislocations virtually independent to the temperature. On the other hand, the CRSS for super dislocations exhibits a weak positive temperature dependence from room temperature up to 573 K and decreases in higher temperatures.

scholarly journals Breakdown of the Schmid Law in BCC Molybdenum Related to the Effect of Shear Stress Perpendicular to the Slip Direction

2005 ◽  
Vol 482 ◽  
pp. 123-126 ◽  
Author(s):  
R. Gröger ◽  
V. Vitek
Keyword(s):  
Shear Stress ◽  
Dislocation Motion ◽  
Peierls Stress ◽  
Shear Stresses ◽  
Slip Direction ◽  
Burgers Vector ◽  
Long Time ◽  
Schmid Factor ◽  
Critical Resolved Shear Stress ◽  
Negative Sense

The breakdown of the Schmid law in bcc metals has been known for a long time. The asymmetry of shearing in the slip direction 〈111〉 in the positive and negative sense, respectively, commonly identified with the twinning-antitwinning asymmetry, is undoubtedly one of the reasons. However, effect of stress components other than the shear stress in the slip direction may be important. In this paper we investigate by atomistic modeling the effect of shear stresses perpendicular to the Burgers vector on the glide of a/2〈111〉 screw dislocations. We show that these shear stresses can significantly elevate or reduce the critical resolved shear stress (CRSS) in the direction of the Burgers vector needed for the dislocation motion, i.e. the Peierls stress. This occurs owing to the changes of the core induced by these stresses. This effect may be the reason why slip systems with smaller Schmid factors may be preferred over that with the largest Schmid factor.

Plastic Deformations in Single Crystals of FePd with the L10 Structure

2008 ◽  
Vol 1128 ◽  
Author(s):  
Katsushi Tanaka ◽  
Wang Chen ◽  
Kyosuke Kishida ◽  
Norihiko L. Okamoto ◽  
Haruyuki Inui
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Yield Stress ◽  
Room Temperature ◽  
Positive Temperature ◽  
Plastic Deformations ◽  
L10 Structure ◽  
Critical Resolved Shear Stress

AbstractCompressive deformations of L10-ordered single crystals of FePd have been investigated from room temperature to 873 K. The critical resolved shear stress for superlattice dislocations is hard to determine resulting from buckling that occurs after a small amount of conventional plastic deformation. The CRSS for superlattice dislocations determined from yield stress is significantly larger than that of ordinary dislocations. The CRSS for octahedral glide of ordinary and superlattice dislocations are virtually independent of the temperature, and the positive temperature dependence of the yield stress is not observed for both, ordinary and superlattice dislocations, by the present experiments.

Anisotropy in the hardness of single crystals

1971 ◽  
Vol 322 (1548) ◽  
pp. 73-88 ◽  
Keyword(s):  
Crystal Structure ◽  
Shear Stress ◽  
Single Crystals ◽  
Dislocation Motion ◽  
Slip Systems ◽  
Maximum Hardness ◽  
Indentation Process ◽  
Wide Range ◽  
Knoop Indentation ◽  
Active Slip

The results of this work, and those published by other researchers who have used Knoop indentation measurements, confirm that the nature of anisotropy in hardness is essentially determined by the crystal structure and the primary slip systems which accommodate dislocation motion during indentation. Materials belonging to the same class of crystal structure and having common slip systems possess similar anisotropic properties. The varying extent of work-hardening or fracture, associated with indentations, does not appear to influence the anisotropy— although twinning on the basal planes of hexagonal closepacked metals may have a significant effect. An analysis of the indentation process is presented which establishes a clear relationship between the ‘effective resolved shear stress’ (t 0 '), in the bulk of the crystal beneath the indenter, and the observed hardness. Directions which correspond to the minimum values of t' e , on specific crystallographic surfaces, are those of maximum hardness and conversely. The analysis is shown to be equally applicable to a wide range of crystalline solids including nonmetallic materials, of various crystal structure, and typical f.c.c., b.c.c. and c.p.h. metals. Finally, anisotropy in hardness can be used to identify active slip systems in those crystals where it is possible for dislocations to move on more than one system.

Springback Suppression of AZ31 Magnesium Alloy Sheet in Draw Bending at Elevated Temperature

2019 ◽  
Vol 794 ◽  
pp. 127-132
Author(s):  
Takashi Katahira ◽  
Takeshi Uemori ◽  
Tetsuya Yoshida ◽  
Michihiro Takiguchi ◽  
Tetsuo Naka ◽  
...  
Keyword(s):  
Shear Stress ◽  
Elevated Temperature ◽  
Room Temperature ◽  
Relaxation Effect ◽  
Alloy Sheet ◽  
Az31 Magnesium Alloy Sheet ◽  
Forming Condition ◽  
Effects Of Temperature ◽  
Draw Bending ◽  
Critical Resolved Shear Stress

In recent years, warm forming of magnesium sheets has been investigated by many researchers since the ductility of the sheets becomes considerably higher due to low CRSS (critical resolved shear stress) at high temperatures (e.g., [1]-[3]). In the present research, the springback of AZ31 magnesium sheet was investigated by performing a draw-bending experiment at several temperatures from 20 °C (room temperature) to 200 °C at drawing speeds ranging from 0.01 to 1.0 mm/s. From the experiment, it was found that the springback was remarkably reduced at 200 °C, especially at a low forming speed, since the flow stress was very low under such a forming condition, and furthermore, the stress relaxation effect was dominant. The effects of temperature and forming speed on springback were discussed.

The slip modes of titanium and the effect of purity on their occurrence during tensile deformation of single crystals

1954 ◽  
Vol 226 (1165) ◽  
pp. 216-226 ◽  
Keyword(s):  
Shear Stress ◽  
Slip System ◽  
Single Crystals ◽  
Tensile Deformation ◽  
Interstitial Impurity ◽  
Slip Systems ◽  
Slip Planes ◽  
Critical Resolved Shear Stress ◽  
Interstitial Elements

Single-crystal test specimens of van Arkel titanium were obtained by a modification of the strain anneal technique.The modes of slip have been identified as (101̄0) [112̄0],(101̄1) [112̄0], and (0001) [112̄0]. It has been shown that not only does the interstitial impurity affect the magnitude of the critical resolved shear stress but also the relative values for the three slip systems. (101̄0) is the principal slip system and is favoured by increasing purity. A possible mechanism for the role of oxygen and nitrogen in this effect is put forward wherein it is shown that the interstitial sites occupied are such that interstitial elements render slip more difficult on two of the three slip planes in titanium.

Hydrogen-enhanced dislocation velocities in Ni3Al single crystals

2000 ◽  
Vol 15 (1) ◽  
pp. 7-9 ◽  
Author(s):  
C. B. Jiang ◽  
S. Patu ◽  
Q. Z. Lei ◽  
C. X. Shi
Keyword(s):  
Activation Energy ◽  
Shear Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Dislocation Motion ◽  
Dislocation Velocity ◽  
Dislocation Mobility ◽  
Preliminary Results ◽  
Etch Pit

The average dislocation velocity in hydrogenated Ni3Al single crystals was directly measured as a function of resolved shear stress (RSS) at room temperature (293 K) by the etch-pit technique. It was found that the dislocation velocity with hydrogen is about 5–25 times faster than that without hydrogen for the same RSS, and hydrogen decreases activation energy for dislocation motion in Ni3Al single crystals. The reason hydrogen can enhance dislocation velocity in this compound is briefly discussed. These preliminary results quantitatively provide the first evidence of hydrogen-enhancing dislocation mobility in Ni3Al material.

SLIP PLANES IN Fe – 3% Si SINGLE CRYSTALS DEFORMED AT 77 °K

1967 ◽  
Vol 45 (2) ◽  
pp. 1031-1040 ◽  
Author(s):  
B. Šesták ◽  
N. Zárubová ◽  
V. Sládek
Keyword(s):  
Shear Stress ◽  
Large Deviations ◽  
Single Crystal ◽  
Single Crystals ◽  
Room Temperature ◽  
Four Point Bending ◽  
Crystallographic Slip ◽  
Slip Planes

Macroscopic slip planes were determined on specimens of different orientations, cut from a single crystal of Fe – 3% Si alloy after slow deformation [Formula: see text] by four-point bending at 77 °K. On the compression side of the specimens with orientations [Formula: see text] the slip planes were found to be very close to those with maximum resolved shear stress. On the compression side of the specimens with [Formula: see text] and on the tension side of specimens with [Formula: see text] (except the specimens with χ = ±30°) either crystallographic slip along {110} planes or large deviations of slip planes from maximum resolved shear stress planes to {110} planes were observed. The ψ(χ) curves obtained at 77 °K are compared with those obtained similarly at room temperature. The ψ(χ) curves for 77 °K cannot be explained microscopically on the basis of the composite slip on {110} and {112} planes if only the effect of the slip sense is assumed.

scholarly journals Room-temperature deformation of single crystals of ZrB2 and TiB2 with the hexagonal AlB2 structure investigated by micropillar compression

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zhenghao Chen ◽  
Bhaskar Paul ◽  
Sanjib Majumdar ◽  
Norihiko L. Okamoto ◽  
Kyosuke Kishida ◽  
...  
Keyword(s):  
Single Crystals ◽  
Plastic Flow ◽  
Room Temperature ◽  
Resolve Shear Stress ◽  
Temperature Deformation ◽  
Slip Systems ◽  
Compression Tests ◽  
Plastic Deformation Behavior ◽  
Bulk Single Crystals ◽  
Micropillar Compression

AbstractThe plastic deformation behavior of single crystals of two transition-metal diborides, ZrB2 and TiB2 with the AlB2 structure has been investigated at room temperature as a function of crystal orientation and specimen size by micropillar compression tests. Although plastic flow is not observed at all for their bulk single crystals at room temperature, plastic flow is successfully observed at room temperature by the operation of slip on {1$${\bar{1}}$$ 1 ¯ 00}<11$${\bar{2}}$$ 2 ¯ 3> in ZrB2 and by the operation of slip on {1$${\bar{1}}$$ 1 ¯ 00}<0001> and {1$${\bar{1}}$$ 1 ¯ 00}<11$${\bar{2}}$$ 2 ¯ 0> in TiB2. Critical resolve shear stress values at room temperature are very high, exceeding 1 GPa for all observed slip systems; 3.01 GPa for {1$${\bar{1}}$$ 1 ¯ 00}<11$${\bar{2}}$$ 2 ¯ 3> slip in ZrB2 and 1.72 GPa and 5.17 GPa, respectively for {1$${\bar{1}}$$ 1 ¯ 00}<0001> and {1$${\bar{1}}$$ 1 ¯ 00}<11$${\bar{2}}$$ 2 ¯ 0> slip in TiB2. The identified operative slip systems and their CRSS values are discussed in comparison with those identified in the corresponding bulk single crystals at high temperatures and those inferred from micro-hardness anisotropy in the early studies.

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